I just bought Sunday Missal , but remembered was given one from 1975. Is it the same readings because that's all I bought it for. If it is I will get refund and put that money towards getting daily Missal.

As you know, all the prayers of the 2011 Missal have been re-translated. In addition, new propers for saints have been added and various other small revisions that came in the second and third Typical Editions of the Latin Roman Missal. In this respect, the 1975 Missal is severely deficient.

The lectionary has been revised since 1975. At least once. The New American Bible is used in dioceses of the United States; I believe the most recent revision was 1997 - here is an article. The readings may be from the same parts of the Bible, but the wording will no longer match exactly.

By all means, keep the new edition. The 1975 edition is suitable for wrapping fish, rolling cigarettes, or as a historical example of Things the Church Will Never Do Again to give to a student in RCIA.

*Just kidding about the treatment of that old Missal. Treat it with respect as a vessel of Sacred Scripture.